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(**************************************************************************)
(*                                                                        *)
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(*  Copyright (C) 2010-2012                                               *)
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(*    François Bobot                                                      *)
(*    Jean-Christophe Filliâtre                                           *)
(*    Claude Marché                                                       *)
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(*    Guillaume Melquiond                                                 *)
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(*    Andrei Paskevich                                                    *)
(*                                                                        *)
(*  This software is free software; you can redistribute it and/or        *)
(*  modify it under the terms of the GNU Library General Public           *)
(*  License version 2.1, with the special exception on linking            *)
(*  described in file LICENSE.                                            *)
(*                                                                        *)
(*  This software is distributed in the hope that it will be useful,      *)
(*  but WITHOUT ANY WARRANTY; without even the implied warranty of        *)
(*  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.                  *)
(*                                                                        *)
(**************************************************************************)

open Why3
open Util
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open Ident
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open Ty
open Term
open Decl
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open Theory
open Env
open Ptree
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open Mlw_dtree
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open Mlw_ty
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open Mlw_ty.T
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open Mlw_expr
open Mlw_decl
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open Mlw_pretty
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open Mlw_module
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open Mlw_wp
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open Mlw_dty
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(** errors *)

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exception DuplicateProgVar of string
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exception DuplicateTypeVar of string
(*
exception PredicateExpected
exception TermExpected
exception FSymExpected of lsymbol
exception PSymExpected of lsymbol
exception ClashTheory of string
exception UnboundTheory of qualid
exception UnboundType of string list
*)
exception UnboundTypeVar of string
exception UnboundSymbol of string list

let error = Loc.error
let errorm = Loc.errorm

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let qloc = Typing.qloc
let print_qualid = Typing.print_qualid
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let () = Exn_printer.register (fun fmt e -> match e with
  | DuplicateTypeVar s ->
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      Format.fprintf fmt "Type parameter %s is used twice" s
  | DuplicateProgVar s ->
      Format.fprintf fmt "Parameter %s is used twice" s
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(*
  | PredicateExpected ->
      Format.fprintf fmt "syntax error: predicate expected"
  | TermExpected ->
      Format.fprintf fmt "syntax error: term expected"
  | FSymExpected ls ->
      Format.fprintf fmt "%a is not a function symbol" Pretty.print_ls ls
  | PSymExpected ls ->
      Format.fprintf fmt "%a is not a predicate symbol" Pretty.print_ls ls
  | ClashTheory s ->
      Format.fprintf fmt "Clash with previous theory %s" s
  | UnboundTheory q ->
      Format.fprintf fmt "unbound theory %a" print_qualid q
  | UnboundType sl ->
      Format.fprintf fmt "Unbound type '%a'"
        (Pp.print_list Pp.dot Pp.pp_print_string) sl
*)
  | UnboundTypeVar s ->
      Format.fprintf fmt "unbound type variable '%s" s
  | UnboundSymbol sl ->
      Format.fprintf fmt "Unbound symbol '%a'"
        (Pp.print_list Pp.dot Format.pp_print_string) sl
  | _ -> raise e)

(* TODO: let type_only = Debug.test_flag Typing.debug_type_only in *)

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type denv = {
  uc     : module_uc;
  locals : (tvars * dity) Mstr.t;
  tvars  : tvars;
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  uloc   : Ptree.loc option;
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}
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let create_denv uc = {
  uc     = uc;
  locals = Mstr.empty;
  tvars  = empty_tvars;
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  uloc   = None;
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}
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(** Typing type expressions *)

let rec dity_of_pty ~user denv = function
  | Ptree.PPTtyvar id ->
      create_user_type_variable id
  | Ptree.PPTtyapp (pl, p) ->
      let dl = List.map (dity_of_pty ~user denv) pl in
      let x = Typing.string_list_of_qualid [] p in
      begin
        try
          let its = ns_find_it (get_namespace denv.uc) x in
          its_app ~user its dl
        with Not_found -> try
          let ts = ns_find_ts (Theory.get_namespace (get_theory denv.uc)) x in
          ts_app ts dl
        with Not_found ->
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          errorm ~loc:(qloc p) "unbound symbol %a" print_qualid p
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      end
  | Ptree.PPTtuple pl ->
      ts_app (ts_tuple (List.length pl)) (List.map (dity_of_pty ~user denv) pl)
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(** Typing program expressions *)

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let dity_int  = ts_app ts_int  []
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let dity_real = ts_app ts_real []
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let dity_bool = ts_app ts_bool []
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let dity_unit = ts_app ts_unit []
let dity_mark = ts_app ts_mark []
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let unify_loc loc fn_unify x1 x2 =
  try fn_unify x1 x2 with
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    | TypeMismatch (ity1,ity2) ->
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        errorm ~loc "This expression has type %a, \
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          but is expected to have type %a"
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        Mlw_pretty.print_ity ity2 Mlw_pretty.print_ity ity1
    | exn -> error ~loc exn

let expected_type ?(weak=false) e dity =
  unify_loc e.de_loc (unify ~weak) dity e.de_type
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let rec extract_labels labs loc e = match e.Ptree.expr_desc with
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  | Ptree.Enamed (Ptree.Lstr s, e) -> extract_labels (Slab.add s labs) loc e
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  | Ptree.Enamed (Ptree.Lpos p, e) -> extract_labels labs (Some p) e
  | Ptree.Ecast  (e, ty) ->
      let labs, loc, d = extract_labels labs loc e in
      labs, loc, Ptree.Ecast ({ e with Ptree.expr_desc = d }, ty)
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  | e -> labs, loc, e
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let rec decompose_app args e = match e.Ptree.expr_desc with
  | Eapply (e1, e2) -> decompose_app (e2 :: args) e1
  | _ -> e, args
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(* namespace lookup *)

let uc_find_ls uc p =
  let x = Typing.string_list_of_qualid [] p in
  ns_find_ls (Theory.get_namespace (get_theory uc)) x

let uc_find_prgs uc p =
  let x = Typing.string_list_of_qualid [] p in
  ns_find_ps (get_namespace uc) x

exception LS of lsymbol

let uc_find_ps_or_ls uc p =
  let x = Typing.string_list_of_qualid [] p in
  try ns_find_ps (get_namespace uc) x with Not_found ->
  (* we didn't find p in the module namespace *)
  let ls = ns_find_ls (Theory.get_namespace (get_theory uc)) x in
  (* and we did find it in the pure theory *)
  if Mid.mem ls.ls_name (get_known uc) then
    (* but it was defined in a program declaration! *)
    error ~loc:(qloc p) (HiddenPLS ls);
  (* fine, it's just a pure lsymbol *)
  raise (LS ls)

let uc_find_ps uc p =
  try uc_find_ps_or_ls uc p with LS _ -> raise Not_found

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(* record parsing *)

let parse_record uc fll =
  let pl = match fll with
    | [] -> raise EmptyRecord
    | (pl,_)::_ -> pl in
  let its = match pl.pl_args with
    | [{ vtv_ity = { ity_node = Ityapp (its,_,_) }}] -> its
    | _ -> raise (BadRecordField pl.pl_ls) in
  let cs, pjl = match find_constructors (get_known uc) its with
    | [cs,pjl] -> cs, List.map (exn_option (BadRecordField pl.pl_ls)) pjl
    | _ -> raise (BadRecordField pl.pl_ls) in
  let pjs = List.fold_left (fun s pj -> Sls.add pj.pl_ls s) Sls.empty pjl in
  let flm = List.fold_left (fun m (pj,v) -> let pj = pj.pl_ls in
    if not (Sls.mem pj pjs) then raise (BadRecordField pj) else
      Mls.add_new (DuplicateRecordField (cs.pl_ls,pj)) pj v m)
    Mls.empty fll
  in
  cs,pjl,flm

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let find_field uc (p,e) = try match uc_find_ps uc p with
  | PL pl -> (pl,e)
  | _ -> errorm ~loc:(qloc p) "bad record field %a" print_qualid p
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  with Not_found -> errorm ~loc:(qloc p) "unbound symbol %a" print_qualid p
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let find_pure_field uc (p,e) = try uc_find_ls uc p, e
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  with Not_found -> errorm ~loc:(qloc p) "unbound symbol %a" print_qualid p
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let pure_record uc = function
  | [] -> raise Decl.EmptyRecord
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  | (p,_)::_ -> (try ignore (uc_find_ps uc p); false with Not_found -> true)
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let hidden_pl ~loc pl =
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  { de_desc = DEglobal_pl pl;
    de_type = specialize_plsymbol pl;
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    de_loc  = loc; de_lab = Slab.empty }
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let hidden_ls ~loc ls =
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  { de_desc = DEglobal_ls ls;
    de_type = specialize_lsymbol ls;
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    de_loc  = loc; de_lab = Slab.empty }
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(* helper functions for let-expansion *)
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let test_var e = match e.de_desc with
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  | DElocal _ | DEglobal_pv _ -> true
  | _ -> false

let mk_var e =
  if test_var e then e else
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  { de_desc = DElocal "q";
    de_type = e.de_type;
    de_loc  = e.de_loc;
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    de_lab  = Slab.empty }
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let mk_id s loc =
  { id = s; id_loc = loc; id_lab = [] }

let mk_dexpr desc dity loc labs =
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  { de_desc = desc; de_type = dity; de_loc = loc; de_lab = labs }
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let mk_let ~loc ~uloc e (desc,dity) =
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  if test_var e then desc, dity else
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  let loc = def_option loc uloc in
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  let e1 = mk_dexpr desc dity loc Slab.empty in
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  DElet (mk_id "q" loc, false, e, e1), dity
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(* patterns *)

let add_var id dity denv =
  let tvars = add_tvars denv.tvars dity in
  let locals = Mstr.add id.id (tvars,dity) denv.locals in
  { denv with locals = locals; tvars = tvars }

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let specialize_qualid uc p = try match uc_find_ps_or_ls uc p with
  | PV pv -> DEglobal_pv pv, specialize_pvsymbol pv
  | PS ps -> DEglobal_ps ps, specialize_psymbol  ps
  | PL pl -> DEglobal_pl pl, specialize_plsymbol pl
  | PX xs -> errorm ~loc:(qloc p) "unexpected exception symbol %a" print_xs xs
  with
  | LS ls -> DEglobal_ls ls, specialize_lsymbol ls
  | Not_found -> errorm ~loc:(qloc p) "unbound symbol %a" print_qualid p

let find_xsymbol uc p = try match uc_find_prgs uc p with
  | PX xs -> xs
  | _ -> errorm ~loc:(qloc p) "exception symbol expected"
  with Not_found -> errorm ~loc:(qloc p) "unbound symbol %a" print_qualid p
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let find_variant_ls uc p = try match uc_find_ls uc p with
  | { ls_args = [u;v]; ls_value = None } as ls when ty_equal u v -> ls
  | ls -> errorm ~loc:(qloc p) "%a is not a binary relation" Pretty.print_ls ls
  with Not_found -> errorm ~loc:(qloc p) "unbound symbol %a" print_qualid p
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let find_global_vs uc p = try match uc_find_prgs uc p with
  | PV pv -> Some pv.pv_vs
  | _ -> None
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  with Not_found -> None

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let rec dpattern denv ({ pat_loc = loc } as pp) = match pp.pat_desc with
  | Ptree.PPpwild ->
      PPwild, create_type_variable (), denv
  | Ptree.PPpvar id ->
      let dity = create_type_variable () in
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      PPvar (Denv.create_user_id id), dity, add_var id dity denv
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  | Ptree.PPpapp (q,ppl) ->
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      let sym, dity = specialize_qualid denv.uc q in
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      dpat_app denv loc (mk_dexpr sym dity loc Slab.empty) ppl
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  | Ptree.PPprec fl when pure_record denv.uc fl ->
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      let kn = Theory.get_known (get_theory denv.uc) in
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      let fl = List.map (find_pure_field denv.uc) fl in
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      let cs,pjl,flm = Loc.try2 loc Decl.parse_record kn fl in
      let wild = { pat_desc = Ptree.PPpwild; pat_loc = loc } in
      let get_val pj = Mls.find_def wild pj flm in
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      dpat_app denv loc (hidden_ls ~loc cs) (List.map get_val pjl)
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  | Ptree.PPprec fl ->
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      let fl = List.map (find_field denv.uc) fl in
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      let cs,pjl,flm = Loc.try2 loc parse_record denv.uc fl in
      let wild = { pat_desc = Ptree.PPpwild; pat_loc = loc } in
      let get_val pj = Mls.find_def wild pj.pl_ls flm in
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      dpat_app denv loc (hidden_pl ~loc cs) (List.map get_val pjl)
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  | Ptree.PPptuple ppl ->
      let cs = fs_tuple (List.length ppl) in
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      dpat_app denv loc (hidden_ls ~loc cs) ppl
  | Ptree.PPpor (lpp1, lpp2) ->
      let pp1, dity1, denv = dpattern denv lpp1 in
      let pp2, dity2, denv = dpattern denv lpp2 in
      unify_loc lpp2.pat_loc unify dity1 dity2;
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      PPor (pp1, pp2), dity1, denv
  | Ptree.PPpas (pp, id) ->
      let pp, dity, denv = dpattern denv pp in
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      PPas (pp, Denv.create_user_id id), dity, add_var id dity denv
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and dpat_app denv gloc ({ de_loc = loc } as de) ppl =
  let add_pp lp (ppl, tyl, denv) =
    let pp, ty, denv = dpattern denv lp in
    pp::ppl, (lp.pat_loc,ty)::tyl, denv in
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  let ppl, tyl, denv = List.fold_right add_pp ppl ([],[],denv) in
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  let pp = match de.de_desc with
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    | DEglobal_pl pl -> Mlw_expr.PPpapp (pl, ppl)
    | DEglobal_ls ls -> PPlapp (ls, ppl)
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    | DEglobal_pv pv -> errorm ~loc "%a is not a constructor" print_pv pv
    | DEglobal_ps ps -> errorm ~loc "%a is not a constructor" print_ps ps
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    | _ -> assert false
  in
  let res = create_type_variable () in
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  Loc.try2 gloc unify_list de.de_type tyl res;
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  pp, res, denv

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(* specifications *)

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let dbinders denv bl =
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  let hv = Hashtbl.create 3 in
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  let dbinder (id,gh,pty) (denv,bl,tyl) =
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    if Hashtbl.mem hv id.id then errorm "duplicate argument %s" id.id;
    Hashtbl.add hv id.id ();
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    let dity = match pty with
      | Some pty -> dity_of_pty ~user:true denv pty
      | None -> create_type_variable () in
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    add_var id dity denv, (id,gh,dity)::bl, dity::tyl
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  in
  List.fold_right dbinder bl (denv,[],[])
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let deff_of_peff uc pe =
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  { deff_reads  = pe.pe_reads;
    deff_writes = pe.pe_writes;
    deff_raises = List.map (fun (gh,q) -> gh, find_xsymbol uc q) pe.pe_raises; }
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let dxpost uc ql = List.map (fun (q,f) -> find_xsymbol uc q, f) ql

let rec dtype_c denv tyc =
  let tyv, dity = dtype_v denv tyc.pc_result_type in
  { dc_result = tyv;
    dc_effect = deff_of_peff denv.uc tyc.pc_effect;
    dc_pre    = tyc.pc_pre;
    dc_post   = fst tyc.pc_post;
    dc_xpost  = dxpost denv.uc (snd tyc.pc_post); },
  dity

and dtype_v denv = function
  | Tpure pty ->
      let dity = dity_of_pty ~user:true denv pty in
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      DSpecV (false,dity), dity
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  | Tarrow (bl,tyc) ->
      let denv,bl,tyl = dbinders denv bl in
      let tyc,dity = dtype_c denv tyc in
      DSpecA (bl,tyc), make_arrow_type tyl dity
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let dvariant uc = function
  | Some (le, Some q) -> [le, Some (find_variant_ls uc q)]
  | Some (le, None) -> [le, None]
  | None -> []
(* TODO: accept a list of variants in the surface language
  List.map (fun (le,q) -> le, Util.option_map (find_variant_ls uc) q) var
*)

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(* expressions *)
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let de_unit ~loc = hidden_ls ~loc (fs_tuple 0)

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let de_app loc e el =
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  let res = create_type_variable () in
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  let tyl = List.map (fun a -> (a.de_loc, a.de_type)) el in
  Loc.try2 loc unify_list e.de_type tyl res;
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  DEapply (e, el), res

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let rec dexpr denv e =
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  let loc = e.Ptree.expr_loc in
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  let labs, uloc, d = extract_labels Slab.empty denv.uloc e in
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  let denv = { denv with uloc = uloc } in
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  let d, ty = de_desc denv loc d in
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  let loc = def_option loc uloc in
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  mk_dexpr d ty loc labs
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and de_desc denv loc = function
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  | Ptree.Eident (Qident {id=x}) when Mstr.mem x denv.locals ->
      (* local variable *)
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      let tvs, dity = Mstr.find x denv.locals in
      let dity = specialize_scheme tvs dity in
      DElocal x, dity
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  | Ptree.Eident p ->
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      specialize_qualid denv.uc p
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  | Ptree.Eapply (e1, e2) ->
      let e, el = decompose_app [e2] e1 in
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      let el = List.map (dexpr denv) el in
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      de_app loc (dexpr denv e) el
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  | Ptree.Elet (id, gh, e1, e2) ->
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      let e1 = dexpr denv e1 in
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      let dity = e1.de_type in
      let tvars = match e1.de_desc with
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        | DEfun _ -> denv.tvars
        | _ -> add_tvars denv.tvars dity in
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      let locals = Mstr.add id.id (tvars, dity) denv.locals in
      let denv = { denv with locals = locals; tvars = tvars } in
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      let e2 = dexpr denv e2 in
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      DElet (id, gh, e1, e2), e2.de_type
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  | Ptree.Eletrec (rdl, e1) ->
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      let rdl = dletrec denv rdl in
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      let add_one denv (_, { id = id }, _, dity, _) =
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        { denv with locals = Mstr.add id (denv.tvars, dity) denv.locals } in
      let denv = List.fold_left add_one denv rdl in
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      let e1 = dexpr denv e1 in
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      DEletrec (rdl, e1), e1.de_type
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  | Ptree.Efun (bl, tr) ->
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      let lam, dity = dlambda denv bl None tr in
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      DEfun lam, dity
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  | Ptree.Ecast (e1, pty) ->
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      let e1 = dexpr denv e1 in
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      expected_type e1 (dity_of_pty ~user:false denv pty);
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      e1.de_desc, e1.de_type
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  | Ptree.Enamed _ ->
      assert false
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  | Ptree.Esequence (e1, e2) ->
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      let e1 = dexpr denv e1 in
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      expected_type e1 dity_unit;
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      let e2 = dexpr denv e2 in
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      DElet (mk_id "_" loc, false, e1, e2), e2.de_type
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  | Ptree.Eif (e1, e2, e3) ->
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      let e1 = dexpr denv e1 in
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      expected_type e1 dity_bool;
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      let e2 = dexpr denv e2 in
      let e3 = dexpr denv e3 in
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      expected_type e3 e2.de_type;
      DEif (e1, e2, e3), e2.de_type
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  | Ptree.Etuple el ->
      let ls = fs_tuple (List.length el) in
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      let el = List.map (dexpr denv) el in
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      de_app loc (hidden_ls ~loc ls) el
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  | Ptree.Erecord fl when pure_record denv.uc fl ->
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      let kn = Theory.get_known (get_theory denv.uc) in
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      let fl = List.map (find_pure_field denv.uc) fl in
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      let cs,pjl,flm = Loc.try2 loc Decl.parse_record kn fl in
      let get_val pj = match Mls.find_opt pj flm with
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        | Some e -> dexpr denv e
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        | None -> error ~loc (Decl.RecordFieldMissing (cs,pj)) in
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      de_app loc (hidden_ls ~loc cs) (List.map get_val pjl)
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  | Ptree.Erecord fl ->
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      let fl = List.map (find_field denv.uc) fl in
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      let cs,pjl,flm = Loc.try2 loc parse_record denv.uc fl in
      let get_val pj = match Mls.find_opt pj.pl_ls flm with
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        | Some e -> dexpr denv e
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        | None -> error ~loc (Decl.RecordFieldMissing (cs.pl_ls,pj.pl_ls)) in
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      de_app loc (hidden_pl ~loc cs) (List.map get_val pjl)
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  | Ptree.Eupdate (e1, fl) when pure_record denv.uc fl ->
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      let e1 = dexpr denv e1 in
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      let e0 = mk_var e1 in
      let kn = Theory.get_known (get_theory denv.uc) in
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      let fl = List.map (find_pure_field denv.uc) fl in
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      let cs,pjl,flm = Loc.try2 loc Decl.parse_record kn fl in
      let get_val pj = match Mls.find_opt pj flm with
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        | Some e -> dexpr denv e
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        | None ->
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            let loc = Loc.dummy_position in
            let d, dity = de_app loc (hidden_ls ~loc pj) [e0] in
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            mk_dexpr d dity loc Slab.empty in
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      let res = de_app loc (hidden_ls ~loc cs) (List.map get_val pjl) in
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      mk_let ~loc ~uloc:denv.uloc e1 res
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  | Ptree.Eupdate (e1, fl) ->
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      let e1 = dexpr denv e1 in
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      let e0 = mk_var e1 in
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      let fl = List.map (find_field denv.uc) fl in
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      let cs,pjl,flm = Loc.try2 loc parse_record denv.uc fl in
      let get_val pj = match Mls.find_opt pj.pl_ls flm with
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        | Some e -> dexpr denv e
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        | None ->
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            let loc = Loc.dummy_position in
            let d, dity = de_app loc (hidden_pl ~loc pj) [e0] in
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            mk_dexpr d dity loc Slab.empty in
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      let res = de_app loc (hidden_pl ~loc cs) (List.map get_val pjl) in
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      mk_let ~loc ~uloc:denv.uloc e1 res
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  | Ptree.Eassign (e1, q, e2) ->
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      let fl = { expr_desc = Eident q; expr_loc = loc } in
      let e1 = { expr_desc = Eapply (fl,e1); expr_loc = loc } in
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      let e1 = dexpr denv e1 in
      let e2 = dexpr denv e2 in
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      expected_type ~weak:true e2 e1.de_type;
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      DEassign (e1, e2), dity_unit
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  | Ptree.Econstant (ConstInt _ as c) ->
      DEconstant c, dity_int
  | Ptree.Econstant (ConstReal _ as c) ->
      DEconstant c, dity_real
  | Ptree.Enot e1 ->
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      let e1 = dexpr denv e1 in
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      expected_type e1 dity_bool;
      DEnot e1, dity_bool
  | Ptree.Elazy (op, e1, e2) ->
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      let e1 = dexpr denv e1 in
      let e2 = dexpr denv e2 in
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      expected_type e1 dity_bool;
      expected_type e2 dity_bool;
      DElazy (op, e1, e2), dity_bool
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  | Ptree.Ematch (e1, bl) ->
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      let e1 = dexpr denv e1 in
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      let res = create_type_variable () in
      let branch (pp,e) =
        let ppat, dity, denv = dpattern denv pp in
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        unify_loc pp.pat_loc unify e1.de_type dity;
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        let e = dexpr denv e in
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        expected_type e res;
        ppat, e in
      DEmatch (e1, List.map branch bl), res
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  | Ptree.Eraise (q, e1) ->
      let res = create_type_variable () in
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      let xs = find_xsymbol denv.uc q in
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      let dity = specialize_xsymbol xs in
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      let e1 = match e1 with
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        | Some e1 -> dexpr denv e1
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        | None when ity_equal xs.xs_ity ity_unit -> de_unit ~loc
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        | _ -> errorm ~loc "exception argument expected" in
      expected_type e1 dity;
      DEraise (xs, e1), res
  | Ptree.Etry (e1, cl) ->
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      let e1 = dexpr denv e1 in
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      let branch (q, id, e) =
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        let xs = find_xsymbol denv.uc q in
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        let dity = specialize_xsymbol xs in
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        let id, denv = match id with
          | Some id -> id, add_var id dity denv
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          | None -> mk_id "void" loc, denv in
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        let e = dexpr denv e in
        expected_type e e1.de_type;
        xs, id, e
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      in
      let cl = List.map branch cl in
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      DEtry (e1, cl), e1.de_type
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  | Ptree.Eabsurd ->
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      DEabsurd, create_type_variable ()
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  | Ptree.Eassert (ak, lexpr) ->
      DEassert (ak, lexpr), dity_unit
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  | Ptree.Emark (id, e1) ->
      let e1 = dexpr denv e1 in
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      DEmark (id, e1), e1.de_type
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  | Ptree.Eany tyc ->
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      let tyc, dity = dtype_c denv tyc in
      DEany tyc, dity
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  | Ptree.Eghost e1 ->
      let e1 = dexpr denv e1 in
      DEghost e1, e1.de_type
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  | Ptree.Eabstract (e1, (q,xq)) ->
      let e1 = dexpr denv e1 in
      let xq = dxpost denv.uc xq in
      DEabstract (e1, q, xq), e1.de_type
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  | Ptree.Eloop ({ loop_invariant = inv; loop_variant = var }, e1) ->
      let e1 = dexpr denv e1 in
      let var = dvariant denv.uc var in
      expected_type e1 dity_unit;
      DEloop (var,inv,e1), e1.de_type
  | Ptree.Efor (id, efrom, dir, eto, inv, e1) ->
      let efrom = dexpr denv efrom in
      let eto = dexpr denv eto in
      let denv = add_var id dity_int denv in
      let e1 = dexpr denv e1 in
      expected_type efrom dity_int;
      expected_type eto dity_int;
      expected_type e1 dity_unit;
      DEfor (id,efrom,dir,eto,inv,e1), e1.de_type
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and dletrec denv rdl =
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  (* add all functions into environment *)
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  let add_one denv (_,id,_,_,_,_) =
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    let res = create_type_variable () in
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    add_var id res denv, res in
  let denv, tyl = Util.map_fold_left add_one denv rdl in
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  (* then type-check all of them and unify *)
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  let type_one (loc, id, gh, bl, var, tr) res =
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    let lam, dity = dlambda denv bl var tr in
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    Loc.try2 id.id_loc unify dity res;
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    loc, id, gh, dity, lam in
  List.map2 type_one rdl tyl
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and dlambda denv bl var (p, e, (q, xq)) =
  let denv,bl,tyl = dbinders denv bl in
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  let e = dexpr denv e in
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  let var = dvariant denv.uc var in
  let xq = dxpost denv.uc xq in
  (bl, var, p, e, q, xq), make_arrow_type tyl e.de_type
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(** stage 2 *)
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type lenv = {
  mod_uc   : module_uc;
  let_vars : let_var Mstr.t;
  log_vars : vsymbol Mstr.t;
  log_denv : Typing.denv;
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}

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let create_lenv uc = {
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  mod_uc   = use_export_theory uc Mlw_wp.th_mark;
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  let_vars = Mstr.empty;
  log_vars = Mstr.empty;
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  log_denv = Typing.denv_empty_with_globals (find_global_vs uc);
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}

let rec dty_of_ty ty = match ty.ty_node with
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  | Ty.Tyapp (ts, tyl) -> Denv.tyapp ts (List.map dty_of_ty tyl)
  | Ty.Tyvar v -> Denv.tyuvar v
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let create_post lenv x ty f =
  let res = create_vsymbol (id_fresh x) ty in
  let log_vars = Mstr.add x res lenv.log_vars in
  let log_denv = Typing.add_var x (dty_of_ty ty) lenv.log_denv in
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  let f = Typing.type_fmla (get_theory lenv.mod_uc) log_denv log_vars f in
  create_post res f
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let create_pre lenv f =
  Typing.type_fmla (get_theory lenv.mod_uc) lenv.log_denv lenv.log_vars f

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let create_variant lenv (t,r) =
  let t =
    Typing.type_term (get_theory lenv.mod_uc) lenv.log_denv lenv.log_vars t in
  { v_term = t; v_rel = r }
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let add_local x lv lenv = match lv with
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  | LetA _ ->
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      { lenv with let_vars = Mstr.add x lv lenv.let_vars }
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  | LetV pv ->
      let dty = dty_of_ty pv.pv_vs.vs_ty in
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      { mod_uc   = lenv.mod_uc;
        let_vars = Mstr.add x lv lenv.let_vars;
        log_vars = Mstr.add x pv.pv_vs lenv.log_vars;
        log_denv = Typing.add_var x dty lenv.log_denv }
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exception DuplicateException of xsymbol

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let binders lenv bl =
  let binder lenv (id, ghost, dity) =
    let vtv = vty_value ~ghost (ity_of_dity dity) in
    let pv = create_pvsymbol (Denv.create_user_id id) vtv in
    add_local id.id (LetV pv) lenv, pv in
  Util.map_fold_left binder lenv bl

let xpost lenv xq =
  let add_exn m (xs,f) =
    let f = create_post lenv "result" (ty_of_ity xs.xs_ity) f in
    Mexn.add_new (DuplicateException xs) xs f m in
  List.fold_left add_exn Mexn.empty xq

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(* TODO: devise a good grammar for effect expressions *)
let rec get_eff_expr lenv { pp_desc = d; pp_loc = loc } = match d with
  | Ptree.PPvar (Ptree.Qident {id=x}) when Mstr.mem x lenv.let_vars ->
      begin match Mstr.find x lenv.let_vars with
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        | LetV pv -> pv.pv_vtv
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        | LetA _ -> errorm ~loc "%s must be a first-order value" x
      end
  | Ptree.PPvar p ->
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      begin try match uc_find_prgs lenv.mod_uc p with
        | PV pv -> pv.pv_vtv
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        | _ -> errorm ~loc:(qloc p) "%a is not a variable" print_qualid p
      with Not_found -> errorm ~loc "unbound variable %a" print_qualid p end
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  | Ptree.PPapp (p, [le]) ->
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      let vtv = get_eff_expr lenv le in
      let quit () = errorm ~loc:le.pp_loc "This expression is not a record" in
      let pjm = match vtv.vtv_ity.ity_node with
        | Ityapp (its,_,_) ->
            let pjl = match find_constructors (get_known lenv.mod_uc) its with
              | (_,pjl)::_ -> pjl | _ -> quit () in
            let add_pj m pj = match pj with
              | Some { pl_ls = ls; pl_args = [vtva]; pl_value = vtvv } ->
                  Mls.add ls (vtva.vtv_ity, vtvv) m
              | Some _ -> assert false
              | None -> m in
            List.fold_left add_pj Mls.empty pjl
        | Itypur (ts,_) ->
            let kn = Theory.get_known (get_theory lenv.mod_uc) in
            let pjl = match Decl.find_constructors kn ts with
              | (_,pjl)::_ -> pjl | _ -> quit () in
            let add_pj m pj = match pj with
              | Some ({ ls_args = [tya]; ls_value = Some tyv } as ls) ->
                  Mls.add ls (ity_of_ty tya, vty_value (ity_of_ty tyv)) m
              | Some _ -> assert false
              | None -> m in
            List.fold_left add_pj Mls.empty pjl
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        | _ -> quit ()
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      in
      let itya, vtvv =
        try Mls.find (uc_find_ls lenv.mod_uc p) pjm with Not_found ->
          errorm ~loc:(qloc p) "%a is not a field name" print_qualid p in
      let sbs = unify_loc loc (ity_match ity_subst_empty) itya vtv.vtv_ity in
      let mut = Util.option_map (reg_full_inst sbs) vtvv.vtv_mut in
      let ghost = vtv.vtv_ghost || vtvv.vtv_ghost in
      vty_value ~ghost ?mut (ity_full_inst sbs vtvv.vtv_ity)
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  | Ptree.PPcast (e,_) | Ptree.PPnamed (_,e) ->
      get_eff_expr lenv e
  | _ ->
      errorm ~loc "unsupported effect expression"

let get_eff_regs lenv fn eff ghost le =
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  let vtv = get_eff_expr lenv le in
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  let ghost = ghost || vtv.vtv_ghost in
  match vtv.vtv_mut, vtv.vtv_ity.ity_node with
  | Some reg, _ ->
      fn eff ?ghost:(Some ghost) reg
  | None, Ityapp (its,_,(_::_ as regl)) ->
      let add_arg regs vtv = match vtv.vtv_mut with
        | Some r when vtv.vtv_ghost -> Sreg.add r regs | _ -> regs in
      let add_cs regs (cs,_) = List.fold_left add_arg regs cs.pl_args in
      let csl = find_constructors (get_known lenv.mod_uc) its in
      let ghost_regs = List.fold_left add_cs Sreg.empty csl in
      let add_reg eff reg0 reg =
        let ghost = ghost || Sreg.mem reg0 ghost_regs in
        fn eff ?ghost:(Some ghost) reg
      in
      List.fold_left2 add_reg eff its.its_regs regl
  | _ ->
      errorm ~loc:le.pp_loc "mutable expression expected"

let eff_of_deff lenv deff =
  let add_read eff (gh,e) = get_eff_regs lenv eff_read eff gh e in
  let eff = List.fold_left add_read eff_empty deff.deff_reads in
  let add_write eff (gh,e) = get_eff_regs lenv eff_write eff gh e in
  let eff = List.fold_left add_write eff deff.deff_writes in
  let add_raise eff (gh,xs) = eff_raise eff ~ghost:gh xs in
  let eff = List.fold_left add_raise eff deff.deff_raises in
  eff

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let rec type_c lenv gh vars dtyc =
  let result = type_v lenv gh vars dtyc.dc_result in
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  let ty = match result with
    | SpecV v -> ty_of_ity v.vtv_ity
    | SpecA _ -> ty_unit in
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  let eff = eff_of_deff lenv dtyc.dc_effect in
  (* reset every new region in the result *)
  let eff = match result with
    | SpecV v ->
        let rec add_reg r eff =
          if reg_occurs r vars then eff else eff_reset (add_ity r.reg_ity eff) r
        and add_ity ity eff = Sreg.fold add_reg ity.ity_vars.vars_reg eff in
        add_ity v.vtv_ity eff
    | SpecA _ -> eff in
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  { c_pre    = create_pre lenv dtyc.dc_pre;
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    c_effect = eff;
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    c_result = result;
    c_post   = create_post lenv "result" ty dtyc.dc_post;
    c_xpost  = xpost lenv dtyc.dc_xpost; }

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and type_v lenv gh vars = function
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  | DSpecV (ghost,v) ->
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      let ghost = ghost || gh in
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      SpecV (vty_value ~ghost (ity_of_dity v))
  | DSpecA (bl,tyc) ->
      let lenv, pvl = binders lenv bl in
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      let add_pv s pv = vars_union s pv.pv_vtv.vtv_vars in
      let vars = List.fold_left add_pv vars pvl in
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      SpecA (pvl, type_c lenv gh vars tyc)
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(* expressions *)

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let vty_ghostify gh vty =
  if gh && not (vty_ghost vty) then vty_ghostify vty else vty

let e_ghostify gh e =
  if gh && not (vty_ghost e.e_vty) then e_ghost e else e

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let rec expr lenv de =
  let loc = de.de_loc in
  let e = Loc.try3 loc expr_desc lenv loc de in
  e_label ~loc de.de_lab e

and expr_desc lenv loc de = match de.de_desc with
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  | DElocal x ->
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      assert (Mstr.mem x lenv.let_vars);
      begin match Mstr.find x lenv.let_vars with
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      | LetV pv -> e_value pv
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      | LetA ps -> e_cast ps (vty_of_dity de.de_type)
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      end
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  | DElet (x, gh, { de_desc = DEfun lam }, de2) ->
      let def = expr_fun lenv x gh lam in
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      let lenv = add_local x.id (LetA def.rec_ps) lenv in
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      let e2 = expr lenv de2 in
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      e_rec [def] e2
  | DEfun lam ->
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      let x = mk_id "fn" loc in
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      let def = expr_fun lenv x false lam in
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      let e2 = e_cast def.rec_ps (VTarrow def.rec_ps.ps_vta) in
      e_rec [def] e2
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  (* FIXME? (ghost "lab" fun x -> ...) loses the label "lab" *)
  | DEghost { de_desc = DEfun lam } ->
      let x = mk_id "fn" loc in
      let def = expr_fun lenv x true lam in
      let e2 = e_cast def.rec_ps (VTarrow def.rec_ps.ps_vta) in
      e_rec [def] e2
  | DElet (x, gh, de1, de2) ->
      let e1 = e_ghostify gh (expr lenv de1) in
      begin match e1.e_vty with
        | VTarrow { vta_ghost = true } when not gh ->
            errorm ~loc "%s must be a ghost function" x.id
        | _ -> ()
      end;
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      let def1 = create_let_defn (Denv.create_user_id x) e1 in
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      let lenv = add_local x.id def1.let_var lenv in
      let e2 = expr lenv de2 in
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      e_let def1 e2
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  | DEletrec (rdl, de1) ->
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      let rdl = expr_rec lenv rdl in
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      let add_rd { rec_ps = ps } = add_local ps.ps_name.id_string (LetA ps) in
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      let e1 = expr (List.fold_right add_rd rdl lenv) de1 in
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      e_rec rdl e1
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  | DEapply (de1, del) ->
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      let el = List.map (expr lenv) del in
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      begin match de1.de_desc with
        | DEglobal_pl pls -> e_plapp pls el (ity_of_dity de.de_type)
        | DEglobal_ls ls  -> e_lapp  ls  el (ity_of_dity de.de_type)
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        | _               -> e_app (expr lenv de1) el
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      end
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  | DEglobal_pv pv ->
      e_value pv
  | DEglobal_ps ps ->
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      e_cast ps (vty_of_dity de.de_type)
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  | DEglobal_pl pl ->
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      e_plapp pl [] (ity_of_dity de.de_type)